Magnetic lock switch for starter and ignition circuits



D. COLLINS Oct. 16, 1956 MAGNETIC LOCK SWITCH FOR STARTER AND IGNITIONCIRCUITS 2 Sheets-Sheet 1 Filed June 29, 1951 Dag/as (Bo/32 22:

ATTORNEYS Oct. 16, 1956 MAGNETIC LOCK Filed Julie 29, 1951 D. COLLINS2,767,278

SWITCH FOR STARTER AND IGNITION CIRCUITS 2 Sheets-Sheet 2 \\Y c A\\\T BOQ /46 YAMM Z ATTOR N EYS United States Patent MAGNETIC LOCK SWITCH FORSTARTER AND IGNITION CIRCUITS Douglas Collins, Salisbury, N. C.

Application June 29, 1951, Serial No. 234,172

17 Claims. (Cl. 200-87) This invention pertains to a combined startingand ignition circuit control, especially for automotive vehicles or thelike, and has for its principal object to provide a unitarycontrol-switch mechanism and lock which will enable the starting andignition circuits to be controlled by a single key, and to be energizedin the desired relationship by a single manually operatedinstrumentality.

A further object of the invention is to provide a lock switch havingmeans to prevent or discourage the unauthorized energization of thestarting and ignition circuits, and hence of the vehicle, and which willbe substantially immune to methods of lock picking and the like commonlyemployed by thieves.

Still another object of the invention is to provide a lock switchoperated by a removable key and so arranged that the insertion of theproper key in the lock energizes the ignition circuit of the vehicle,and a further movement (of one kind or another) of the same key willenergize the starter motor circuit, thus simplifying the operation ofstarting the engine of an automobile or other vehicle.

An additional object of the invention is to provide a device of the kindjust described, so arranged that the key must be removed from the lockswitch in order to deenergize the ignition circuit, and thus to minimizethe possibility that the key will be inadvertently left in the lock whenthe owner leaves the vehicle.

Yet another object of my invention is to provide a switch and lock foroperation by means of a key formed partly of magnetized elements ormagnets, such magnets being so disposed that the lock switchnevertheless cannot be operated by an ordinary magnet or magnetizedobject in the hands of an unauthorized person.

A further object of the invention is to provide a lock switch whoseinterior working portions are completely sealed off from the keyholeslot, so that they cannot be manipulated by mechanical means inserted inthe keyhole slot or groove.

An additional object of the invention is to provide a lock switch andmagnetic key of such design that a large number of combinations can beobtained, and at very low cost, so that operation of a particular switchcan be effected by a relatively small number of the total keysmanufactured.

The above and other objects and advantages of the invention will best beunderstood from the following detailed specification of certainpreferred and exemplary embodiments thereof, taken in connection withthe appended drawings, in which:

Fig. 1 is a perspective view of one embodiment of the lock switch of theinvention shown mounted upon the dashboard or instrument panel of avehicle or the like, and with the control key shown withdrawn from thelock.

Fig. 2 is a longitudinal vertical sectional view of the lock shown inFig. l, and with the two electric switches in deenergized position,

Fig. 3 is a view similar to Fig. 2, but with the key ingizing both theignition circuit and the starting motor circuit,

Fig. 4 is a view similar to Fig. 3, but with the key retracted to aposition in which the starting motor circuit has been deenergized, whilethe ignition circuit remains connected,

Fig. 5 is a schematic wiring diagram showing the relation between thelock switch of the invention to the usual control circuits of thevehicle,

Fig. 6 is a longitudinal sectional view of a modified form of lockswitch embodying the principles of the invention,

Fig. 7 is a perspective view of a key used with the form of lock switchshown in Fig. 6

Fig. 8 is a view, lock, and

Fig. 9 is a view similar to Fig. 6 but showing a magnetic control for acylinder lock.

Referring now to Figs. 1 to 4 of the drawings, which illustrate a firstembodiment of the invention, the lock switch is shown as comprising acylindrical body of casing 10 shown as formed of electrically insulatedmaterial; the use of such material simplifies the provision of thenecessary insulation for the electric switch elements contained in thecasing, but it is perfectly feasible to form this casing of metallicmaterial, so long as such material is non-magnetic in nature. Metalscommonly used for die casting are suitable, and in such case, of course,the switch elements will be secured to the casing by suitable insulatedsupports in a manner well known in the electric switch art. As shown inFig. 1, the body or casing 10 is adapted to be mounted in an apertureformed in the usual dashboard or instrument panel 12 of a motor vehicleor the like, and to this end the casing 10 may have an enlarged frontplate or escutcheon 14, which may be secured to the panel 12 by screwsor the like.

As best shown in Fig. 2, a key passageway 16 extends from the front ofthe device into its interior, and is formed of any suitablecross-section to receive a corresponding key 18. The forward end ofpassageway or slot 16 may be provided with a cut-out 20 adapted toreceive a lug 22 on key 18, and by changing shape and location of theparts 20 and 22, and the shape and dimensions of the passageway 16 andthe body of the partly broken away, of a modified key, a large number ofcombinations may be provided.

serted fully into the lock switch in condition for ener- The lock switchof the invention provides for the control of both the ignition circuitand the starting motor circuit of the vehicle with which it is used, andin order to accomplish this double control by simple and easily operatedmeans, the invention provides two separate circuit making and breakingswitches in the lock switch, at least one of these being controlled by apermanent magnet incorporated in the structure of the key. In the formof the invention shown in Figs. 1 to 4, both of these switches aremagnetically controlled, and the parts are so arranged that theinsertion of the key into the switch to a first position (in which itwill remain unless removed) energizes the ignition circuit, while afurther movement of the key into the passageway (for example, againstthe tension of a spring) operates to energize the starter motor of theengine. Upon the release of the manual pressure required for thisadditional movement of the key, the key is restored by the springpressure to its first condition, in which the starter circuit isdeenergized while the ignition circuit remains in running condition.Since it is necessary to withdraw the key from the slot, or at least toinitiate its withdrawal, in order to stop the engine by breaking theignition circuit, the possibility that the key will accidentally beallowed to remain in the lock is greatly reduced. This feature isdesirable in order to reduce thefts resulting from the thoughtless actof leaving the key in a conventional automobile lock after the igni tionhas been turned 01?.

es 24 and 26, suitably secured to casing and provided with connectingscrews 28 and 39 for connection in series between the battery of thevehicle and the primary wind g of the ignition coil. The switchconsisting of contact elements 2 and is contained within a recess 32.formed in the casing 19 but closed off from the key slot or passageway16 for a reason to be described below. Contact spring 24, which is themovable contact of this switch, carries at its free end a yoke 34between whose parallel arms is pivoted a magnetic armature 36, formed ofsome material such as soft ironwhich is attracted by a permanent magnet,but which does not retain substantial magnetization when the permanentmagnet is removed from "its v lty. The pivotal mounting for armature 36provides for seesaw motion with respect to the movable contact 24. Thewall or partition which separates recess 32 from passageway it? containstwo slugs of similar soft iron, designated'by numeral 38, which act totransmit the magnetic lines of force from the key (to be describedbelow), to the two ends of th pivoted armature 36. Since the attractiveforces on these two ends of the armature will be equal, the armature 36will be moved bodily downward when the magnetic key is inserted in thelock to a position symmetrical with the slot, and will, therefore,deflect contact spring 24 until it touches contact spring 26, therebycompleting the circuit to the ignition coil. If a key is used which hasspaced poles not matched with the slugs Sb-that is, not suitablyconstructed to operate the particular lock-the forces on opposite sidesof the pivotal mounting for the armature will not be balanced, and thearmature will tilt without producing any closing force on the contact24.

The other switch shown in Fig. 2 also comprises contact springs andterminal screws which may be duplicates of those just described, but inthis case the contact springs are located in another recess or cavitywhich is separated from the passageway 16 by a wall structure whichincludes the magnetically permeable portions 42. in this case, themovable contact spring also terminates in a yoke carrying a pivotedarmature numbered 44, and which is also adapted to be moved bodilyupward when the key 13 is inserted in the lock, under the attraction ofa second magnet carried by said key. Armature 44 is likewise pivoted forsee-saw motion and, unless a key having properly spaced poles isprovided, the forces acting around the pivot will not be substantiallybalanced, and the armature will tilt without closing the switch.

In order to permit this second switch to be closed only when the startermotor of the engine is to be energized, the invention provides for an.additional movement of the key into the key slot to operate this secondswitch. As seen in Fig. 2, the inner end of slot 16 is closed by aspring-pressed stop plate 46 urged toward the left in that figure by acoil spring 48, for a distance determined by the engagement of the head56, of a bolt 01' pin secured to plate as, with the rear surface of thecasing 1i Fig. 3 illustrates the parts when key 18 has been inserted inthe passageway 16 to the fullest extent possible, thus compressingspring 4% as the plate 46 is pushed to the right by the key, stop head53 moving away from the rear wall of casing 15). The key 18 has integraltherewith a pair of relatively strong permanent magnets 52 and 54 whichmay for example be made of permanently magnetized Alnico or similarhighly magnetic material. As shown also in Fig, 1, each of the magnets52 and 54 has active pole faces which are spaced along the length of thebody of key 19. Thus, when the key is inserted fully in the lock asshown in Fig. 3, the two poles of magnet 52 lie against the soft ironslugs in the wall separating the key from upper pivoted armature 36, andthe lines of magnetic force therefore pass through the armature 3d anddraw it bodily downward, closing the ignition control switch in themanner described above in connection with Fig. 2. Also, with the keyinserted to this maximum extent, the poles of magnet 54 are in alignmentwith the soft iron slugs adjacent armature 44 of the lower switch, andthis armature is attracted upwardly so as to close the starter circuitand start the engine. Although in this position the poles 52 ar notexerting equal forces about the pivot of armature 36, this is notnecessary, because the armature cannot tilt with contacts 24 and 26closed.

When key 18 is released, it will be moved slightly to the left under thepressure of spring 48, and thereafter will remain in the position shownin Fig. 4 of the drawings. In this position, and due to the length ofthe slugs 38 associated with the ignition switch, the magneticattraction of magnet 52 upon armature 36 remains in etfect, and theignition circuit is maintained in its closed or energized condition.However, the size and positioning of slugs 42 associated with thestarter switch is such that magnet dd finds no magnetically permeablepath for the flux which formerly attracted armature 44, and the latteris released, thereby deenergizing the starter motor of the vehicle.

From the above description it will be seen that neither of the switchesof the device can be operated by any mechanical instrumentality insertedin the keyway 16, because all the movable portions of both switches areblocked oif from this keyway. Also, the use of pivoted armatures such as36 and 44, instead of simple nonpivoted armatures, prevents theoperation of either switch by the insertion of a simple magnet,magnetized blade or the like. Any such device will operate upon one endonly of either of the armatures 36 and 44, causing a simple tilting ofthe armatures upon its pivot yoke (as shown in dash lines in Fig.2),'and will be ineffective to cause movement of the armature as a unitor symmetrical displacement thereof, such as is required to producecircuit-closing motion of the movable contact spring. While I havedescribed the use of permeable slugs 38 and 42 of different sizes toprovide for the separate energiz ation of the ignition and startercircuits, it is clear that the same separation of functions can also beachieved by the proper positioning of slugs of the same size, or byarranging the magnets 52 and 54 so that their pole pieces are ofdifferent lengths, and so on. Obviously, the material of which the keyitself is made must be non-magnetic, such as a non-magnetic metal, andthe permanent magnets 52 and '54 may be secured in place therein in anydesired manner, or may even be imbedded in the material forming the bodyof the key.

Fig. 5 of the drawings illustrates by a. schematic wiring diagram theway in which the lock switch of the invention is related to theconventional elements constituting the starting and ignition circuits ofa vehicle or the like. In this figure, numeral 10 designates the casingof "the lock switch, and numeral 18 again designates the control key.The main car battery, usually but not necessarily a six-volt storagebattery, is shown at numeral 58, and has one side grounded, as byconnection to the vehicle frame. The other side or terminal of thisbattery is connected by a lead 60 to one terminal of each of the switchelements of my invention, and

7 also to the solenoid switch or control 62 of the starter motor 64. Theother terminal of the starting motor control 62 is connected to theswitch 10 at the terminal which is closed when the armature 44 (of Figs.2 to 4) is attracted. Numeral 66 designates the usual high-tension coilor transformer of the ignition system, whose primary winding isconnected to lead 60 through the other switch element of the lockswitch; that is, to the terminals 28 and 30. The other side of theprimary of coil or transformer 66 is connected to the battery 58 bybeing grounded through the ignition points in the usual way, and thesecondary winding leads'through the usual distributor 68 to the sparkplugs of the engine, generally designated by numeral 70. The operationof the circuit will be clearly understood from the description alreadygiven of the manner in which the insertion of key 18 first energizes theignition circuit, and then, upon a further movement thereof into thelock, energizes the starter motor. The system as described isconstructed around the Bendix type of starter system, utilizing aselfengaging starter motor drive under control of a sole noid switch,but it is clearly equally well adapted for the control of the Delco-Remyor solenoid shift type of starter control, as well understood by thoseskilled in the art.

Figs. 6 and 7 of the drawing illustrate a modified embodiment of theinvention, in which only one of the switches of the invention ismagnetically operated, the other being of a mechanically or cam operatedtype. In these figures, numeral 72 designates the control key generally,the same having in this case a shank or body portion which isapproximately cylindrical, with a single magnet 74 on one side, andproviding two spaced pole faces 76 and 78 in a manner similar to themagnet 52 of Figs. 1 to 4. The opposite side of the shank is flat tenedas indicated at 80, and the end face of the shank has a rectangularextension or rib 82, for a purpose to be described.

As best shown in Fig. 6, the lock switch of this form of the inventioncomprises a casing 84 of generally the shape utilized in the first formof the invention. The switch elements for controlling the ignitioncircuit again comprise spring tongues or strips indicated by numerals 85and 88, and provided with suitable screw or other terminals forconnection to the external circuit. Switch spring 86 has a pivot yoke 90carrying the magnetizable armature 92 as before, the same beingattracted downward by the magnet 74 whenever the key 72 is inser-ted inthe cylindrical keyway of the lock. In this embodiment, the startercircuit is energized, not by a further movement of the key into thekeyway, but by a slight rotation of the key after it has been inserted.To this end, the movable contact spring of the other switch element,numbered 94, extends through an aperture from recess 96 into the keyway,and is arranged to be deflected into electrical contact with the spring98 upon rotation of the key 72; normally, the flat portion 80 of the keypasses over the spring 94 without deflecting the same, but when the keyis rotated slightly from this position, the contact spring is of coursemoved into contact with the other spring 98 to energize the startercontrol circuit. In order to ensure that the key returns to its normalposition after the starting operation, and with the ignition circuitstill energized, the rectangular rib 82 at its end is disposed to entera rectangular slot transverse to the circular plate 100 mounted forrotation at the end of the keyway, and secured in place as by 'a pin102. A torsion spring 104 is connected between this disc 1% and thecasing of the lock switch to return the plate and key 72 to their normalpositions, as shown in Fig. 6, upon release of the key after thestarting operation has been completed.

In .the embodiment just described, it is of course possible for thecontact spring 94 to be engaged with the fixed contact 98 by means of aninstrument inserted in the keyway, but since the ignition circuit cannotbe so operated (as it requires the special magnetic key formation), thisfeature does not compromise the security of the system as against theft.

Fig. 8 of the drawings illustrates a modified form of lock switch inwhich the movable armature in the lock, and the key, both havepermanently magnetized portions. In this modification, reference numeral110 designates a yoke-shaped armature having permanent magnetic poles112 and 1 14. These permanent poles are normally held away from the softiron slugs 116 to provide an air gap sufiicient to prevent the yoke fromattracting itself against these slugs. A compression spring 118 normallyholds the yoke in the position shown, but obviously any equivalentspring arrangement could be provided for this purpose. The yoke carriesa spring contact blade 124 normally held away from the fixed contacts126, 128.

The key 120 is again provided with an integral permanent magnet 122having magnetic poles which are spaced to cooperate with the soft ironslugs. Thus, when the key is inserted in the position shown, itsmagnetic poles attract the yoke 110 downwardly to operate the contacts,the strengths of the magnetic poles on the yoke and on the key beingsufiicient, when added together, to attract the yoke or armature intocontact with the soft iron slugs. The external circuit is thus completedthrough the terminals connected to the fixed contacts. It will beunderstood that another set of contacts can also be provided, it beingdeemed unnecessary to show these in the drawing.

The principal -.advantage of this construction is that the polarities onthe key must be properly related to those of the yoke in order tooperate the switch, otherwise the yoke would be repulsed. The use ofadditional magnets or poles would provide a greater number ofcombinations.

It is obvious that the principle of a magnetic key control can also beapplied to a lock in such a way that a normally locked cylinder can beunlocked by the magn tic force when the proper key is inserted, thusfreeing the cylinder for rotation to control the starting and ignitioncircuits by means of a connection from the cylinder to externalcontacts. Such a modification is illustrated schematically in Fig. 9, inwhich the key is shown as provided with permanent magnetic portions 132,134, and 136, each having a north and a south pole as described inconnection with the other embodiments. Numeral 139 designates a cylinderwhich can be rotated within the lock casing, but is normally blockedagainst such rotation by the yokes such as 138, each having a lockingpin of hardened steel or the like 140. The locking pin is normally heldin a recess 142 in the lock casing, by spring pressure in a mannersimilar to that already described. When the key 130 is inserted in thelock, the magnet portion 132 pulls yoke 138 downwardly, thus disengagingpin 140 from recess 142 and permitting the cylinder 139 to be rotatedthrough a suitable angle.

In the particular embodiment shown in Fig. 9, there are three of theselocking pins, together with their corresponding yokes and springs, andas will be clear from the figure, various combinations can readily beobtained by altering the number, position and dimensions of the yokesand the corresponding magnet portions of the key. Cylinder 139 may beretained against axial movement in the casing as by a rear plate 144secured to the casing by screws or the like. The cylinder 139 is alsoprovided with a pin 146 which extends through an arcuate slot 148 in thecover plate 144, and the motion of this pin when the cylinder is rotatedcan be utilized to control either the starting or ignition circuit, orpreferably both, in a manner clear from the preceding description.

The invention has been described in connection with two preferred andexemplary embodiments thereof, but it is to be understood that theseembodiments are given by way of illustration and not limitation; otherchanges and modification in the details of the system can also be madewithout departing from the spirit of the invention as defined in theappended claims.

I claim:

1. A lock switch comprising a housing, a pair of switches in saidhousing for controlling independent circuits, means including a magnetickey for operating one of said switches upon insertion of said key insaid lock switch, and means responsive to a rotation of said key,

' 7 after it has been completely inserted, for operating the other saidswitches.

2; The invention in accordance with claim 1, including means in saidcasing for resiliently biasing said key toward a position in which saidother switch is returned to non-operated condition.

3. The invention in accordance with claim 2 in which the last-namedmeans comprises a torsion spring, and means for connecting said springwith said key when the latter is fully inserted in said lock switch.

' 4. A magnetic lock switch comprising a housing, means forming a keyslot in said housing, a switch having spaced contacts within saidhousing, an operating means for said switch including a tiltablearmature mounted intermediate its ends for see-saw motion on saidoperating means and normally spaced from said slot means, the initialspacing between said switch contacts being less than the s, acing ofsaid tiltable' armature from said slot means whereby said operatingmeans is moved to close said switch in response to magnetic forcesacting simultaneously along said armature to produce lineardisplacements of said tiltable armature with respect to said slot means,the space between said tiltable armature and said slot means beinglimited, whereby insufiicient movement is imparted to said operatingmeans to cause operation of said switch by tilting movement of saidtiltable armature in the di- 'rection of said slot means.

5. A magnetic key operated switch comprising, in combination, a pair ofspaced switch contacts including a movable contact, and a magneticallyactuated member mounted intermediate its ends for see-saw motion on saidmovable contact and adapted to operate said switch through said mountingin response to spaced magnetic forces acting simultaneously along saidmember in substantial balance about said see-saw mounting, but not inresponse to magnetic forces applied on one end only to unbalance andtilt said magnetically actuated member.

6. A magnetic key operated switch comprising, in combination, a keyslot, a pair of spaced switch contacts including a movable contact, anda magnetically actuated member mounted intermediate its ends for see-sawmotion on said movable contact and adapted to operate said switchthrough said mounting in response to spaced mag netic forces actingsimultaneously along said magnetically actuated member on opposite sidesof said see-saw mounting, but not in response to magnetic forces appliedat one end only of said magnetically actuated member, and means in saidkey slot to transmit magnetic forces of greater density to the ends ofsaid magnetically actuated member.

7. A magnetic key operated switch comprising, in combination, a pair ofspaced switch contacts including a movable contact, and a magneticallyactuated member mounted intermediate its ends for see-saw motion on saidmovable contact and adapted to operate said switch through said see-sawmounting in response to spaced magnetic forces of opposite polarityacting simultaneously along said member on opposite sides of saidsee-saw mounting, but not in response to magnetic forces appliedsuccessively first to one end of said member and then to the oppositeend of said member.

8. A magnetic key operated switch comprising, in combination, a pair ofspaced switch contacts including a movable contact, and a magneticallyactuated member mounted intermediate its ends for see-saw motion on saidmovable contact and adapted to operate said switch through said sec-sawmounting in response to spaced magnetic forces of opposite polarityacting simultaneously along said member on opposite sides of saidsee-saw mounting, but not in response to magnetic forces appliedsuccessively first to one end of said member and then to the oppositeend of said member, and spaced metal slugs to transmit magnetic forcesto the ends of said member.

9. A magnetic key operated switch comprising, in

combination, a pair of spaced switch contacts including a movablecontact, and a magnetically actuated member mounted intermediate itsends for see-saw motion on said movable contact and adapted to operatesaid switch through said see-saw mounting in response to spaced magneticforces of opposite polarity acting simultaneously along said member onopposite sides in substantial balance about said see-saw mounting, butnot in response to magnetic forces of the same polarity applied tounbalance and tilt said member, and means to transmit magnetic forces ofgreater density to the ends of said member.

10. A magnetic lock switch comprising a housing, means forming a keyslot in said housing, a plurality of switch means in said housingcomprising pairs of spaced switch contacts including a movable contactin each of said pairs, and a. magnetically actuated member mountedintermediate its ends for see-saw motion on each of said movablecontacts and adapted to operate said switches through said mountings inresponse to magnetic forces acting simultaneously along said members,but not in response to magnetic forces acting on only one end of saidmagnetically actuated member, a key member receivable in said slothaving spaced magnetic inserts to apply forces to said magneticallyactuated member on both sides of said see-saw mounting for linearlydisplacing said member when said key is inserted through said slot toactuate said switch means.

11. The combination defined in claim 10 provided with means in said slotf r properly positioning said key for actuation of said switchessequentially and for normally holding said hey positioned to close oneof said switch means.

12. A magnetic lock switch comprising a housing, means forming a keyslot in said housing, a pair of switches in said housing for controllingindependent circuits, one of said switches being a magnetic key operatedswitch comprising a pair of spaced switch contacts including a movablecontact, and a magnetically actuated member mounted intermediate its forsee-saw motion on said movable contact and adapted to operate saidswitch through said mounting in response to spaced magnetic forcesacting simultaneously along said member but not in response to magneticforces acting to unbalance and tilt said magnetically actuated member onsaid seesaw mounting, a magnetic key with spaced magnetic inserts foroperating said first switch by applying magnetic forces to opposite endsof said magnetically actuated member upon insertion of said key in saidslot, and means responsive to rotation of said key after it has beencompletely inserted for operating the other said switch.

13. The combination as defined in claim 12, including means in saidcasing for resiliently biasing said key toward a position in which theother said switch is returned to open condition.

14. The combination as defined in claim 13 in which the last named meanscomprises a torsion spring and means for connecting said spring withsaid key when the latter is fully inserted in said lock switch.

i5. A lock switch comprising a housing, a magnetic key operated switchin said housing comprising a pair of spaced switch contact elementsmovable from open to closed position, and a magnetically actuated membermounted intermediate its ends for see-saw motion on one or" saidcontacts and adapted to operate said switch through said mounting inresponse to magnetic forces acting simultaneously along said member butnot in response to magnetic forces acting to unbalance and tilt said manetically actuated member on said see-saw mounting, and a key foroperating said switch when inserted in said housing including spacedmagnetic inserts in said key for applying balanced op rating forces tosaid opposite ends of said magnetically actuated member and formaintaining said switch closed until the key is removed from thehousing.

16. The combination as defined in claim 15 wherein said magneticallyoperated member is a magnet with spaced poles of opposite polarity.

17. A magnetic key operated switch comprising, in combination, a pair oflaterally spaced switch contacts, a movable switch element adapted tobridge said switch contacts, a magnet secured to said movable contacthaving opposite poles spaced longitudinally of said contact on oppositesides of the mid portion thereof and acting as an actuator for saidswitch, and a resilient, compressible, and flexible spring membersupporting said magnet actuator and said movable switch contactintermediate the ends thereof for limited angular and bodily movement inany direction on said resilient mounting and holding said switch elementspaced from said switch contacts, said actuator being adapted to operatesaid switch in response to spaced magnetic forces of opposite polarityacting simultaneously along said member on opposite sides of saidsee-saw mounting but not in response to magnetic forces of the samepolarity applied along said actuator.

References Cited in the file of this patent UNITED STATES PATENTS FieldApr. 3, 1883 Dowd Mar, 10, 1925 Watson Apr. 21., 1925 Garvin Nov. 9,1926 Brach Dec. 8, 1931 Ractlifie June 21, 1938 Stroud Jan. 22, 1946Cooley Aug. 28, 1951 McLeod Nov. 6, 1951 Cooley May 6, 1952 Fruh Ian. 6,1953 FOREIGN PATENTS Great Britain Apr. 23, 1931 Great Britain Feb. 21,1944

